The invention relates to a method for the reformation of fuels, in particular of heating oil or another liquid fuel, preferably for the purpose of obtaining electrical and thermal energy by means of high temperature fuel cells. The invention also relates to apparatuses for carrying out the method and also to a plant with fuel cells in which the method of the invention is used.
The reformation of hydrocarbons, which are for example present in the form of fuel gas or vaporized heating oil, can be carried out catalytically at around 800° C. with the admixture of water in vapor form and a supply of heat. During the reformation, carbon monoxide and hydrogen arise which, as educts, can be used for electrochemical processes in high temperature fuel cells, for example in the battery of fuel cells as is known from EP-A-0 780 917. This battery contains a cell block with fuel cells which is surrounded by a heat insulating sleeve. An afterburning space is located between the sleeve and the cell block. A reformer (also termed a pre-reformer) which is suitable only for the preparation of a gaseous fuel is arranged in the sleeve. It is connected to a heat exchanger by means of which the heat required for the reformation processes can be supplied to it from exhaust gases.
When air or another oxygen containing gas which is composed of an inert component and of a component consisting of molecular oxygen O2 is admixed to the hydrocarbons a partial oxidation takes place in parallel to the endothermic reformation processes, the partial oxidation is exothermic and water arises as a reaction product. The water formed by the partial oxidation serves as an educt of the reformation. An admixture of water is thus no longer required or only partly required, which is advantageous since water is expensive having regard to the demands made on its purity. However a problem arises when the reformation is carried out together with a partial oxidation, as the following explanations show:
The reformation processes are carried out by a heterogeneous catalysis in a catalytic converter with a uniform structure. The catalytic converter consists of a catalyst support, on the surface of which the catalytically active material, namely a platinum material (in particular platinum, rhodium or palladium), nickel or a mixture of such metals, is applied. The oxidation which takes place simultaneously does so much more quickly then the endothermic reformation reaction; it thus takes place in an inlet region of the catalytic converter in which high temperatures arise as a result of the heat output through the oxidation. These temperatures can result in a deactivation of catalytically active metals, for example by vaporization, and thus damage to the catalytic converter.